Semiconductor device and fabrication method thereof

ABSTRACT

A semiconductor device comprises a metal gate electrode, a passive device and a hard mask layer. The passive device has a poly-silicon element layer. The hard mask layer is disposed on the metal gate electrode and the passive electrode and has a first opening and a second opening substantially coplanar with each other, wherein the metal gate electrode and the poly-silicon element layer are respectively exposed via the first opening and the second opening; and there is a distance between the first opening and the metal gate electrode substantially less than the distance between the second opening and the poly-silicon element layer.

FIELD OF THE INVENTION

The present invention relates to a semiconductor device and thefabricating method thereof, more particularly to a field effecttransistor (FET) with a metal gate and the fabricating method thereof.

BACKGROUND OF THE INVENTION

With the development of the electrical technology, a FET with highintegrity and operation speed is required. As each technology nodesshrink, the dimensions of a FET and the thickness of its gate oxide,however, must be reduced and gate leakage could be more likely triggeredby the reduced gate length.

In order to reduce gate leakage, high dielectric constant (high-k) gateinsulator layers are used and the conventional polysilicon gateelectrode is replaced with a metal gate (MG) electrode to improve thedevice performance as the feature sizes has being decreased.

The conventional technique for fabricating a metal gate transistorincludes the following steps: Firstly a metal-oxide-semiconductor (MOS)transistor with a poly-silicon dummy gate electrode is formed. After theMOS transistor is completed, the dummy gate electrode will be removed byan etching process. Subsequently, a metal layer is deposited in theregion where the dummy gate electrode was originally located, while a MGelectrode of the metal gate transistor is formed.

However, removing the dummy gate and depositing the metal layer mayconversely affect the integration of the metal gate transistor withother semiconductor devices. For example, a poly-silicon layer initiallyused to form the dummy gate electrode of the MOS transistor may be usedto form an element layer of a passive device, such as an electricresistor. To avoid the poly-silicon element layer from damages resultedby the etching process; a photo-resist may be required to mask thepoly-silicon element layer of the electrical resistor before the etchingprocess for removing the dummy gate electrode is carried out, thereby astep height measured from the MG electrode of the metal gate transistorand the element layer of the electrical resistor may occur. Thus certainamount of metal resides may be remained on the peripheral area of theelectrical resistor after the metal deposition and a subsequent metalcontact formation is performed. Accordingly, device performance maydeteriorate.

Therefore, it is necessary to provide an advanced semiconductor deviceand the fabrication method thereof to obviate the drawbacks and problemsencountered from the prior art.

SUMMARY OF THE INVENTION

One aspect of the present invention, a semiconductor device is provided,wherein the semiconductor device comprises a metal gate electrode, apassive device and a hard mask layer. The passive device has apoly-silicon element layer. The hard mask layer is disposed on the metalgate electrode and the passive electrode and has a first opening and asecond opening substantially coplanar with each other. The metal gateelectrode and the poly-silicon element layer are respectively exposedvia the first opening and a second opening, wherein there is a distancebetween the first opening and the metal gate electrode substantiallyless than the distance between the second opening and the poly-siliconelement layer.

In one embodiment of the present invention, the semiconductor devicefurther comprises a substrate, a source/drain structure and a gatedielectric layer. The source/drain structure is formed in the substrateand adjacent to the metal gate electrode. The gate dielectric layer isdisposed between the metal gate electrode and the source/drainstructure.

In one embodiment of the present invention, the gate dielectric layercomprises an interfacial layer (IL) and a high-k dielectric layer. Inone embodiment of the present invention, the passive device is anelectrical resistor. In one embodiment of the present invention, thesemiconductor device further comprises a capping layer disposed betweenthe metal gate electrode and the high-k dielectric layer.

In one embodiment of the present invention, the semiconductor devicefurther comprises a first spacer and a second spacer, wherein the firstspacer comprises a portion of the hard mask layer covered on thesidewalls of the metal gate electrode used to defined the first opening,and the second spacer comprises another portion of the hard mask layercovered on the poly-silicon element layer used to defined the secondopening.

Another aspect of the present invention is to provide a method forfabricating a semiconductor device, wherein the method comprises stepsas follows: A dummy gate with a poly-silicon gate electrode and apassive device having a poly-silicon element layer are firstly provided.A hard mask layer is then formed on the dummy gate and the passivedevice. Next, a first etching process is performed to remove a portionof the hard mask layer to expose a portion of the poly-silicon elementlayer. Subsequently, an inner layer dielectric (ILD) is formed on thedummy gate and the poly-silicon element layer, and the ILD is flattenedby using the hard mask layer as a polishing stop layer. Thereafter, asecond etching process is performed to remove the poly-silicon gateelectrode, and a metal gate electrode is formed on the location wherethe poly-silicon gate electrode was initially disposed.

In one embodiment of the present invention, the first etching processfurther removes a portion of the poly-silicon element layer, whereby arecess is formed in the passive device to expose the remainingpoly-silicon element layer.

In some embodiment of the present invention, the formation of the dummygate and the passive device comprises following steps: A dielectricmaterial layer and a poly-silicon layer are provided in sequence on asubstrate. The dielectric material layer and a poly-silicon layer arethen patterned to form the poly-silicon gate electrode and thepoly-silicon element layer on the patterned dielectric material layer.Subsequently, a first spacer and a second spacer are respectively formedon the poly-silicon gate electrode and the poly-silicon element layer.

In one embodiment of the present invention, the dielectric materiallayer comprises an IL and a high-k dielectric layer stacked in sequenceat the substrate. In one embodiment of the present invention, the methodfurther comprises steps of forming a capping layer disposed between themetal gate electrode and high-k dielectric layer. In one embodiment ofthe present invention, the method further comprises forming a workingfunction layer on the capping layer, prior to the formation of the metalgate electrode.

In one embodiment of the present invention, the method further comprisesforming a source/drain structure by using the dummy gate as a mask,before the second etching process is carried out. In one embodiment ofthe present invention, prior to the formation of the metal gateelectrode, the method further comprises forming a high-k dielectriclayer on the location where the poly-silicon gate electrode wasinitially disposed, and forming at least one working function layer onthe high-k dielectric layer.

In one embodiment of the present invention, the second etching processcomprises a wet etching and a dry etching. In one embodiment of thepresent invention, the steps of flattening the ILD comprise a chemicalmechanism polishing (CMP) process.

In accordance with the aforementioned embodiments of the presentinvention, a semiconductor device in which a metal gate transistor and apassive device are integrated is provided. The process for fabricatingthe semiconductor device comprises steps as follows: A hard mask layeris firstly formed to cover a dummy gate electrode and a passive device.A first etching process is subsequently performed to remove a portion ofthe hard mask layer, so as to expose apportion of a poly-silicon elementlayer of the passive device. Subsequently, a second etching process isperformed to remove the dummy gate electrode. After a metal depositionand a metal planarizaition process are carried a metal gate coplanarwith the passive device is provided.

By performing these two separate etching processes respectively thinningthe poly-silicon element layer and removing the poly-silicon gateelectrode, the passive device and the metal gate can get a coplanarsurface on which metal contacts can be formed without remainingundesired metal residues. Therefore the performance of the semiconductordevice can be improved significantly.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects and advantages of the present invention will becomemore readily apparent to those ordinarily skilled in the art afterreviewing the following detailed description and accompanying drawings,in which:

FIGS. 1A to 1G are cross-sectional views illustrating the method forfabricating a semiconductor device in accordance with one embodiment ofthe present invention.

FIGS. 2A to 2G are cross-sectional views illustrating the method forfabricating a semiconductor device in accordance with another embodimentof the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention is to provide an advanced semiconductor device andthe fabricating method thereof used to integrate a metal gate transistorwith a passive device. The present invention will now be described morespecifically with reference to the following embodiments. It is to benoted that the following descriptions of preferred embodiments of thisinvention are presented herein for purpose of illustration anddescription only. It is not intended to be exhaustive or to be limitedto the precise form disclosed.

FIGS. 1A to 1G are cross-sectional views illustrating the method forfabricating a semiconductor device 100 in accordance with one embodimentof the present invention, wherein the method comprises steps as follows:

A substrate 101 having a dielectric material layer 104, a capping layer120 and a poly-silicon layer 105 sequentially stacked on the substrate101 is provided (see FIG. 1A). In the present embodiment, the dielectricmaterial layer 104 comprises an IL 104 a and high-k dielectric layer 104b sequentially stacked on the substrate 101. The IL 104 a is preferablymade of silicon oxide (SiO₂), silicon nitride (SiN), silicon oxynitride(SiON) or silicon carbonitride (SiCN). The high-k dielectric layer 104 bis preferably made of hafnium silicon, hafnium oxide, hafnium siliconoxide or hafnium silicon oxynitride. The capping layer 120 is preferablymade of titanium nitride (TiN) or tantalum nitride (TaN). In someembodiments of the present invention, at least one hard mask layer (notshown) may be provided on the poly-silicon layer 105.

Next, the dielectric material layer 104 and the poly-silicon layer 105are patterned, whereby a poly-silicon gate electrode 106 and apoly-silicon element layer 107 are respectively formed on the patterneddielectric material layer 104 (thereinafter the portion of the patterneddielectric material layer 104 beneath the poly-silicon gate electrode106 is referred as gate dielectric layer 108). Oxide deposition andoxide etching processes are then performed to form a first spacer 109disposed on the sidewalls of the poly-silicon gate electrode 106 and asecond spacer 110 disposed on the sidewalls of the poly-silicon elementlayer 107, meanwhile a dummy gate 102 and a passive device 103 areformed on the substrate 101. In the present embodiment, the passivedevice 103 is an electrical resistor.

Prior to the formation of the first spacer 109 and the second spacer110, a plurality of light doped drain (LDD) implantation process byusing the poly-silicon gate electrode 106 the gate dielectric layer 108as a mask are performed to make a LDD structure in the substrate 101 andadjacent to the gate dielectric layer 108. After the first spacer 109and the second spacer 110 are formed, a series ion implantationprocesses are then carried out on the LDD structure by using the dummygate 102 as a mask, whereby a source/drain structure 119 is formed inthe substrate 101 (see FIG. 1B.)

Subsequently, a hard mask layer 111 is formed on the dummy gate 102 andthe passive device 103, and a patterned photo-resist 112 is then formedon the hard mask layer 111 to expose a portion of the hard mask layer111 which is disposed over the poly-silicon element layer 107 (see FIG.1C).

A first etching process is performed to remove a portion of the hardmask layer 111, so as to define an opening 111 a on the hard mask layer111 and expose the poly-silicon element layer 107. The hard mask layer111 can be a contact etching stop layer (CESL) made of SiN, SiC or SiCN,and preferably is a SiN multilayer.

In some preferred embodiments, the first etching process may furtherremove a portion of the poly-silicon element layer 107 to formed arecess 113, and the remaining portion of the poly-silicon element layer107 can be exposed from the recess 113 and the opening 111 a (see FIG.1D).

An ILD 114 is formed on the dummy gate 102 and the passive device 103,so as to fill the recess 113. The ILD 114 is then flattened by using thehard mask layer 111 as a polishing stop layer (see FIG. 1E). In thepresent invention, the steps of flattening the ILD 114 comprise achemical mechanism polishing (CMP) process.

After that, a second etching process is performed on the dummy gate 102by using the capping layer 120 as an etching stop layer, to remove aportion of the hard mask layer 111 covered on the dummy gate 102 and thepoly-silicon gate electrode 106, whereby an opening 111 b is define onthe hard mask layer 111, a recess 115 is further formed in the dummygate 102, and the capping layer 120 is exposed via the recess 115 andthe opening 111 b (see FIG. 1F). In some embodiments, the second etchingprocess may comprise a dry etching process and a wet etching process. Inthe present embodiment a dry etching process is firstly applied forremoving the hard mask layer 111; and a wet etching process is thenapplied for removing the poly-silicon gate electrode 106.

At least one working function layer 116, such as a TiN ortitanium/aluminum alloy (TaAl) layer, is then formed on the cappinglayer 104 c. A metal layer is subsequently deposited on the cappinglayer 120, and a metal gate 118 having a metal gate electrode 117 isthen formed after the metal layer is flattened, and meanwhile thesemiconductor device 100 is formed (see FIG. 1G). A subsequent processfor fabricating metal contacts electrically connected to metal lines(not shown) may be performed on the metal gate 118 and the passivedevice 103.

FIGS. 2A to 2G are cross-sectional views illustrating the method forfabricating a semiconductor device 200 in accordance with anotherembodiment of the present invention, wherein the method comprises stepsas follows:

A substrate 201 having a dielectric material layer 204 and apoly-silicon layer 205 sequentially stacked on the substrate 201 isprovided (see FIG. 2A). In the present embodiment, the dielectricmaterial layer 204 is preferably made of SiO₂, SiN, SiON or SiCN.

Next, the dielectric material layer 204 and the poly-silicon layer 205are patterned, whereby a poly-silicon gate electrode 206 and apoly-silicon element layer 207 are respectively formed on the patterneddielectric material layer 204. Oxide deposition and oxide etchingprocesses are then performed to form a first spacer 209 disposed on thesidewalls of the poly-silicon gate electrode 206 and a second spacer 210disposed on the sidewalls of the poly-silicon element layer 207,meanwhile a dummy gate 202 and a passive device 203 (preferably is anelectrical resistor) are formed on the substrate 201.

Prior to the formation of the first spacer 209 and the second spacer210, a plurality of light doped drain (LDD) implantation process areperformed by using the poly-silicon gate electrode 206 the gatedielectric layer 208 as a mask to make a LDD structure in the substrate201 and adjacent to the gate dielectric layer 208. After the firstspacer 209 and the second spacer 210 are formed, a series ionimplantation processes are then carried out on the LDD structure byusing the dummy gate 202 as a mask, whereby a source/drain structure 219is formed in the substrate 201 (see FIG. 2B).

Subsequently, a hard mask layer 211 is formed on the dummy gate 202 andthe passive device 203, and a patterned photo-resist 212 is then formedon the hard mask layer 211 to expose a portion of the hard mask layer211 which is disposed over the poly-silicon element layer 207 (see FIG.2C). The hard mask layer 211 can be a contact etching stop layer (CESL)made of SiN, SiC or SiCN, and preferably is a SiN multilayer.

A first etching process is performed to remove a portion of the hardmask layer 211 and a portion of the poly-silicon element layer 207 todefine an opening 211 a on the hard mask layer 211 and further to form arecess 213 in the passive device 203, whereby the remaining poly-siliconelement layer 207 is exposed via the recess 213 and the opening 211 a(see FIG. 2D).

An ILD 214 is formed on the dummy gate 202 and the passive device 203,so as to fill the recess 213. The ILD 214 is then flattened by using thehard mask layer 211 as a polishing stop layer (see FIG. 2E). In thepresent invention, the steps of flattening the ILD 214 comprise a CMPprocess.

After that, a second etching process is performed by using thedielectric material layer 204 as an etching stop layer to remove aportion of the hard mask layer 211 covered on the dummy gate 202 and thepoly-silicon gate electrode 206, whereby an opening 211 b is define onthe hard mask layer 211, a recess 215 is further formed in the dummygate 202, and the dielectric material layer 204 is exposed via therecess 215 and the opening 211 b (see FIG. 2F). In some embodiments, thesecond etching process may comprise a dry etching process and a wetetching process. In the present embodiment a dry etching process isfirstly applied for removing the hard mask layer 211; and a wet etchingprocess is then applied for removing the poly-silicon gate electrode206.

After the poly-silicon gate electrode is removed, a gate dielectriclayer 208 with high dielectric constant (referred as high-k gatedielectric layer 208) is formed on the dielectric material layer 204exposed from the recess 215 and the opening 211 b. In the presentembodiment, the high-k gate dielectric layer 208 comprises an IL 208 aand the high-k material layer 208 b sequentially stacked on thedielectric material layer 204.

At least one working function layer 216, such as a TiN ortitanium/aluminum alloy (TaAl) layer, is then formed on the high-kmaterial layer 208 b. A metal layer is subsequently deposited on thehigh-k material layer 208 b, a metal gate 218 having a metal gateelectrode 217 is formed after the metal layer is flattened, andmeanwhile the semiconductor device 200 is formed (see FIG. 2G). Asubsequent process for fabricating metal contacts electrically connectedto metal lines (not shown) may be performed on the metal gate 218 andthe passive device 203.

Referring to FIG. 2G again, the semiconductor device 200 of the presentembodiment comprises the metal gate 218, the hard mask layer 211 and thepassive device 203, wherein the hard mask layer 211 is disposed on thesidewalls of the metal gate 218 and the passive device 203 andrespectively conformal with the first spacer 209 of the metal gate 218and the second spacer 210 of the passive device 203.

In addition, the hard mask layer 211 has tow openings, such as opening211 a and opening 211 b, form which the metal gate electrode 217 of themetal gate 218 and the poly-silicon element layer 207 of the passivedevice 203 can be respectively exposed. These two openings 211 a and 211b are substantially coplanar with each other; nevertheless, they arerespectively defined by different etching processes. It is because thatthe hard mask layer 211 is subjected at least one plannarization processafter the two different etching processes, such that the two openingwill be formed on the same plane. In other words, the metal gate 218 andthe passive device 203 have a coplanar base for fabricating the metalcontacts.

It is worthy to note that, since the poly-silicon element layer 207 ofthe passive device 203 is partially removed during the first etchingprocess, the thickness of the poly-silicon element layer 207 is lessthan the total thickness of the metal gate electrode 217, the gatedielectric layer 208 and the working function layer 216 by which thepoly-silicon gate electrode 206 is replaced to form the metal gate 218.Thus after the metal gate electrode 217, the gate dielectric layer 208and the working function layer 216 are planarized, there still exists astep height H between the opening 211 b and the poly-silicon elementlayer 207. In other words, even the openings 211 a and 211 b used forrespectively exposing the metal gate electrode 217 and the poly-siliconelement layer 207 are coplanar with the planarized surface, the distancebetween the opening 215 and the metal gate electrode 217 is still lessthan the distance between the opening 213 and the poly-silicon elementlayer 207.

In accordance with the aforementioned embodiments of the presentinvention, a semiconductor device in which a metal gate transistor and apassive device are integrated is provided. The process for fabricatingthe semiconductor device comprises steps as follows: A hard mask layeris firstly formed to cover a dummy gate electrode and a passive device.A first etching process is subsequently performed to remove a portion ofthe hard mask layer, so as to expose apportion of a poly-silicon elementlayer of the passive device. Subsequently, a second etching process isperformed to remove the dummy gate electrode. After a metal depositionand a metal planarizaition process are carried a metal gate coplanarwith the passive device is provided.

By performing these two separate etching processes respectively thinningthe poly-silicon element layer and removing the poly-silicon gateelectrode, the passive device and the metal gate can get a coplanarsurface on which metal contacts can be formed without remainingundesired metal residues. Therefore the performance of the semiconductordevice can be improved significantly.

While the invention has been described in terms of what is presentlyconsidered to be the most practical and preferred embodiments, it is tobe understood that the invention needs not be limited to the disclosedembodiment. On the contrary, it is intended to cover variousmodifications and similar arrangements included within the spirit andscope of the appended claims which are to be accorded with the broadestinterpretation so as to encompass all such modifications and similarstructures.

1. A semiconductor device comprising: a metal gate electrode, a passivedevice, having a poly-silicon element layer; and a hard mask layercovered on the metal gate electrode and the passive electrode and havinga first opening and a second opening substantially coplanar with eachother, wherein the metal gate electrode and the poly-silicon elementlayer are respectively exposed by the first opening and the secondopening; and there is a distance between the first opening and the metalgate electrode substantially less than a distance between the secondopening and the poly-silicon element layer.
 2. The semiconductor deviceaccording to claim 1, further comprising: a substrate; a source/drainstructure, formed in the substrate and adjacent to the metal gateelectrode; and a gate dielectric layer, disposed between the metal gateelectrode and the source/drain structure.
 3. The semiconductor deviceaccording to claim 1, wherein the gate dielectric layer comprises aninterfacial layer (IL) and a high-k dielectric layer.
 4. Thesemiconductor device according to claim 3, further comprising a cappinglayer disposed between the metal gate electrode and the high-kdielectric layer.
 5. The semiconductor device according to claim 1,wherein the passive device is an electrical resistor.
 6. Thesemiconductor device according to claim 1, further comprising: a firstspace, comprising a portion of the hard mask layer covered on sidewallsof the metal gate electrode used to defined the first opening; and asecond spacer, comprising another portion of the hard mask layer coveredon the poly-silicon element layer used to defined the second opening. 7.A method for fabricating a semiconductor device comprising: providing adummy gate with a poly-silicon gate electrode and a passive devicehaving a poly-silicon element layer; forming a hard mask layer on thedummy gate and the passive device; performing a first etching process toremove a portion of the hard mask layer to expose a portion of thepoly-silicon element layer; forming an inner layer dielectric (ILD) onthe dummy gate and the poly-silicon element layer; flattening the ILD byusing the hard mask layer as a polish stop layer; performing a secondetching process to remove the poly-silicon gate electrode; and forming ametal gate electrode on the location where the poly-silicon gateelectrode was initially disposed.
 8. The method for fabricating thesemiconductor device according to claim 7, wherein the first etchingprocess further removes a portion of the poly-silicon element layer,whereby a recess is formed in the passive device to expose the remainingpoly-silicon element layer.
 9. The method for fabricating thesemiconductor device according to claim 7, wherein the formation of thedummy gate and the passive device comprises: providing a dielectricmaterial layer and a poly-silicon layer stacked in sequence on asubstrate; patterning the dielectric material layer and the poly-siliconlayer to form the poly-silicon gate electrode and the poly-siliconelement layer on the patterned dielectric material layer; and forming afirst spacer and a second spacer respectively on the poly-silicon gateelectrode and the poly-silicon element layer.
 10. The method forfabricating the semiconductor device according to claim 9, wherein thedielectric material layer comprises an IL and a high-k dielectric layerstacked in sequence on the substrate.
 11. The method for fabricating thesemiconductor device according to claim 10, further comprising steps offorming a capping layer disposed between the metal gate electrode andhigh-k dielectric layer.
 12. The method for fabricating thesemiconductor device according to claim 11, further comprising steps offorming a working function layer on the capping layer, prior to theformation of the metal gate electrode.
 13. The method for fabricatingthe semiconductor device according to claim 9, further comprising stepsof forming a source/drain structure by using the dummy gate as a mask,before the second etching process is carried out.
 14. The method forfabricating the semiconductor device according to claim 9, prior to theformation of the metal gate electrode, further comprising: forming ahigh-k dielectric layer on the location where the poly-silicon gateelectrode was initially disposed; and forming at least one workingfunction layer on the high-k dielectric layer.
 15. The method forfabricating the semiconductor device according to claim 7, wherein thesecond etching process comprises a wet etching and a dry etching. 16.The method for fabricating the semiconductor device according to claim7, wherein the steps of flattening the ILD comprise a chemical mechanismpolishing (CMP) process.